Water-based foaming composition-method for making same

ABSTRACT

The invention concerns a water based foaming composition and the method of making it. The composition is optimized in that it contains a surfactant specifically selected according to the polymer also present in the composition. The surfactant and the polymer are selected so that they are oppositely charged. The invention is very useful in drilling or treating wells.

This invention relates to an aqueous foam composition that consists ofan optimized combination of surfactants and polymers that arewater-soluble. The applications of such a foam according to thisinvention vary widely, for example for body care, farming applications,fire-fighting, underground works, such as soil consolidation andoperations in wells that are drilled into the subsoil: drilling,treatment of reservoirs, production of hydrocarbons.

The use of an aqueous foam to replace a well fluid that circulatesthrough a pipe lining that goes down into a well which is drilled intothe ground is known. In some cases, the density of the aqueous fluidthat is used is too high for the type of rock, creating an excessivehydrostatic pressure compared to the fracturing resistance of the rockzones through which the drilling passes. The choice is then made to useaqueous fluids with densities that are reduced by the introduction ofgas, and it is attempted to make the thus lightened fluid homogeneous bycreating the most stable foam possible so that it will have at leastadequate power for cleaning the cuttings.

Document US-5513712 describes a drilling process in which a foam thatcomprises a polymer such as non-cross-linked acrylamide and a surfactantis used, but it does not describe a foaming composition that is stableand optimized by achieving synergy between a specific polymer and aspecific surfactant.

Thus, this invention relates to a water-based foaming composition thatcomprises at least one surfactant and a polymer. The surfactant and thepolymer comprise charges of opposite sign.

The applicant has demonstrated that, surprisingly, it was possible tocontrol the production of a stable foam from a composition that isoptimized in terms of surfactant concentration if a polymer or acopolymer with a charge that is opposite in sign to that of the chargeof the surfactant is combined with said surfactant. A cationic polymeror copolymer is combined with an anionic surfactant; an anionic polymeror copolymer is combined with a cationic surfactant.

The surfactants that can conceivably be used in this invention includeall the standard anionic surfactants, such as the anionic group, or:

carboxylates:

soaps of alkaline metals, alkyl or alkyl ether carboxylates,

N-acylamino acids,

N-acylglutamates,

N-acylpolypeptides,

sulfonates:

alkylbenzenesulfonates,

paraffin sulfonates,

α-olefin sulfonates,

petroleum sulfonates,

lignosulfonates,

sulfosuccinic derivatives,

polynaphthylmethanesulfonates,

alkyl taurides,

sulfates:

alkyl sulfates,

alkyl ether sulfates,

phosphates:

monoalkyl phosphates,

dialkyl phosphates

phosphonates.

As cationic surfactants, it is possible to cite:

alkylamine salts,

quaternary ammonium salts of which nitrogen:

comprises a fatty chain, for example, alkyltrimethyl ortrimethylammonium derivatives, alkyldimethyl benzylammonium derivatives,

comprises two fatty chains,

forms part of a heterocycle, for example, the derivatives of pyridinium,imidazolinium, quinolinium, piperidinium, morpholinium.

All the standard anionic polymers can be used according to thisinvention, for example:

synthetic polymers or copolymers that are derived from:

anionic monomers that contain carboxylate or sulfonate or phosphate orphosphonate groups, such as the monomers acrylate, methacrylate,itaconate, 2-acrylamido-2-methyl-propane, sulfonate, 2-methacryloxyethane sulfonate, 3-acrylamido-3-methyl butanoate, styrene sulfonate,styrene carboxylate, vinyl sulfonate, and maleic acid salts.

synthetic copolymers that are derived from:

an anionic monomer, for example in those that are described above and aneutral monomer, for example, acrylamide, acrylic acid, vinylpyrrolidone, ethylene oxide, propylene oxide, maleic anhydride, vinylalcohol, hydroxyethylacrylate, . . .

natural polymers such as:

cellulose derivatives that are modified negatively, such as CMC,

polysaccharides such as xanthanum, alginate,

starches that are modified negatively,

galactomannanes that are modified negatively.

All the standard cationic polymers can be used according to thisinvention, for example:

synthetic polymers or copolymers that are derived from standard cationicmonomers, i.e., of the following general formula:

R1

C══CH2

R2 where R1 or R2 comprises at least one N atom,

polyethylene imines,

polyamide amines,

polyamines,

synthetic copolymers that are derived from:

cationic monomers and neutral monomers (described above),

natural polymers:

starches that are modified positively, chitosans,

galactomannanes that are modified positively,

cellulose derivatives that are modified positively.

The surfactant can be cationic at a concentration that is less thanabout 5 10⁻³ mol/l, and the polymer can be anionic.

The surfactant can be anionic at a concentration that is less than about5 10⁻³ mol/l, and the polymer can be cationic.

The anionic polymer can be a copolymer such as AM/AMPS, of which thelevel of the charged portion can be between 5 and 40%, and preferablybetween 10 and 25%. The surfactant can be of the DoTAB type.

The anionic polymer can be a natural polymer that is modifiednegatively, for example such as CMC.

The cationic polymer can be a copolymer such as AM/MAPTAC, of which thelevel of the charged portion can be between 5 and 40% and preferablybetween 10 and 25. The surfactant can be of the SDS type.

The invention also relates to a process for producing a foam from water,at least one surfactant, and at least one polymer. In the process, asurfactant and a polymer or a copolymer of opposite charge are combined,and the polymer concentration is determined to obtain a stable foam withas low a surfactant level as possible.

The polymer concentration can be determined based on the charge level ofthe polymer and the concentration of surfactant that is used.Considering the electrostatic nature of the interactions between polymerand surfactant, their respective concentrations can be a function of theionic force of the medium.

The foaming solution can, like well fluid (drilling, completion andworkover), also contain solids (cuttings, neutral colloids, . . . ) orother non-charged water-soluble polymers, anti-corrosion additives, . .. .

This invention will be better understood and its advantages will becomeclearer from reading the tests, by no means limiting, that are describedbelow.

The tests are based mainly on comparing, for different foamcompositions, the two following measurements:

the foam volume VM that is formed from a given volume of foamingsolution and defined stirring conditions, which makes it possible tocharacterize the foaming capacity of the solution,

the drainage rate VD, which makes it possible to characterize thestability of the foam that is formed.

Viscosity was measured at the Newtonian level with a low-gradientviscosimeter.

Operating Procedure:

The foaming solution consists of, at least, a mixture of at least onesurfactant with variable concentration, at least one water-solublepolymer also of variable concentration, and water. The pH is adjusted toabout 9 for all the tests. The foam is obtained from 200 ml of foamingsolution by stirring with a whip. The speed of rotation is set at 2000rpm. As a general rule, the stirring time is about 2 minutes, which issufficient to obtain a homogeneous foam, as well as a maximum volume.

To measure the drainage rate, which is characteristic of the stabilityof the foam, the foam that is obtained is poured into a graduated glassfunnel, and the volume of drained solution is noted based on time. Thedrainage rate is defined from the empirical equation that describes thechanges in the drainage curves (Bikerman j. j. 1973):

V=V₀(1−exp(−kt))

V the drained volume (cm³)

V₀ the volume of the initial

solution (cm³)

t time (minute)

From this equation, k, a flow constant, (min⁻¹) is determined.

Drainage rate VD is defined by

VD=kV₀/2 (cm³/min.)

The lower VD is, the more stable the foam.

Tested Systems:

1. Surfactants:

Dodecyltrimethylammonium bromide (DoTAB): cationic surfactant that hasthe following general formula:

sodium dodecyl sulfate (SDS): anionic surfactant of general formula:

2. Polymers:

Polyacrylamide AM (molecular weight MW about 2.5 10⁶ g/mol).

copolymer acrylamide/acrylamido methyl propane sulfonate AM/AMPS ofgeneral formula:

AM/AMPS 75/25 x=25% and Mw=2.8·10⁶ g/mol

AM/AMPS 90/10 x=10% and Mw=3.2·10⁶ g/mol

carboxymethyl cellulose (CMC). The mean degree of substitution of thecarboxylic groups by the cellulose cycle of the sample that is studiedis close to 1. Its molecular weight is about MW=2.10⁶ g/mol.

copolymer acylamide/methyacrylamido propyltrimethylammonium chlorideAM/MAPTAC of general formula:

Copolymers AM/MAPTAC 75/25 (x=25) and AM/MAPTAC 90/10 (x=10%) havemolecular weights Mw of about 3.10⁶ g/mol.

Test 1: Single Cationic surfactant (DoTAB) DoTAB Polymer VM Viscosity VD(mol/l) (750 ppm) (cm³) (mPa · s) (cm³/min.) 5.10⁻⁵ 0 0 0.88 — 5.10⁻⁴ 00 0.86 — 5.10⁻³ 0 1600 0.85 40 20.10⁻³ 0 2200 0.83 23

These tests show that an adequate quantity of surfactant is needed inorder for the production of a stable foam to take place. At a surfactantconcentration of 5.10⁻³ (mol/l), the foam is formed while being stirred,but it is very unstable.

Test 2: Cationic Surfactant and Polyacrylamide AM (non-ionic) DoTABPolymer VM Viscosity VD (mol/l) (750 ppm) (cm³) (mPa · s) (cm³/min.)5.10⁻⁵ AM 0 1.43 — 5.10⁻⁴ AM 0 1.40 — 5.10⁻³ AM 1000 1.34 — 20.10⁻³ AM1800 1.33 17.2

At a DoTAB concentration of 5.10⁻³ (mol/l), the foam that is formed isdestroyed after less than one minute.

This test shows that for DoTAB surfactant concentrations that are lessthan or equal to about 5.10⁻³ mol/l, it is impossible to form a stablefoam even in the presence of a certain polymer concentration of thepolyacrylamide type.

Starting at 20.10⁻³ mol/l and up of surfactant, the foam that is formedin the presence of the polyacrylamide-type polymer is more stable thanwithout polymer. This is due mainly to the increase in viscosity of thefoaming composition, as the measurements of viscosity confirm.

Test 3: Cationic Surfactant DoTAB and Sulfonated Polyacrylamide DoTABPolymer VM Viscosity VD (mol/l) (750 ppm) (cm³) (mPa · s) (cm³/min.)5.10⁻⁵ AM/AMPS-75/25 500 — 5.10⁻⁴ AM/AMPS-75/25 600 — 5.10⁻³AM/AMPS-75/25 <400 — 20.10⁻³ AM/AMPS-75/25 precipitated — 5.10⁻⁵AM/AMPS-90/10 500 3.09 5 5.10⁻⁴ AM/AMPS-90/10 600 3.05 4.6 5.10⁻³AM/AMPS-90/10 1700 1.22 9 20.10⁻³ AM/AMPS-90/10 precipitated —

With a polymer such as AM/AMPS-75/25, i.e., one that comprises on theorder of 25% of a charge with a sign opposite to that of the charge ofthe surfactant, the foam can form, with between-charge interactions, atconcentrations of less than 5.10⁻³ mol/l of surfactant, and inparticular at concentrations of 5.10⁻⁵ and 5.10⁻⁴ mol/l of surfactant.Starting at and beyond 5.10⁻³ mol/l of surfactant concentration, foamdoes not form because there is precipitation, very likely due toexcessively strong interactions between the charged polymer and thesurfactant. Such a test with a polymer such as AM/AMPS-75/25, however,shows the importance of having opposite charges between surfactant andpolymer for forming a foaming composition.

With a less charged polymer, such as AM/AMPS-90/10 (level of charge10%), it is noted that the foam is produced for concentrations that areless than 5.10⁻³ mol/l of surfactant, as for the polymer with a 25%charge, but for a surfactant concentration of about 5.10⁻³ mol/l, thefoaming composition is greatly optimized since a large and very stablevolume of foam is obtained, taking into account the low drainage ratethat is measured.

Relative to the foam that is formed from a polyacrylamide polymer (test2), the foam volume is comparable, but with a quantity of surfactantthat is four times smaller and, moreover, with the achievement ofgreater stability.

Test 4: Cationic Surfactant DoTAB and Carboxymethylcellulose (AQUAPACproduced by the Aqualon Company) DoTAB Polymer VM Viscosity VD (mol/l)(750 ppm) (cm³) (mPa · s) (cm³/min.) 5.10⁻⁵ CMC 450 — 5.10⁻⁴ CMC 600 —2.4 5.10⁻³ CMC precipitated — 20.10⁻³ CMC precipitated — 22.3

This test shows that the addition of an anionic cellulose naturalpolymer such as carboxymethylcellulose (CMC) with a cationic surfactant(DoTAB) makes it possible to form foam because of between-chargeinteractions, with a surfactant concentration of less than 5.10⁻³ mol/l.The foam that is formed with a concentration of 5.10⁻⁴ mol/l of DoTABand 750 ppm of CMC is very stable. It is verified that an excessivesurfactant concentration hampers the formation of a foam, very likelydue to the excessively strong interactions between the polymer and thesurfactant.

Test 5: Cationic Surfactant DoTAB and Sulfonated PolyacrylamideInfluence of the Presence of Salt. 0.5 g/l of NaCl is added to thesolution. DoTAB Polymer VM Viscosity VD (mol/l) (750 ppm) (cm³) (mPa ·s) (cm³/min.) 5.10⁻⁵ 0 0 — 5.10⁻⁴ 0 0 — 5.10⁻³ 0 1500 — 172 (*) 20.10⁻³0 2200 — 20 5.10⁻⁵ AM/AMPS-90/10 450 8 5.10⁻⁴ AM/AMPS-90/10 700 8 5.10⁻³AM/AMPS-90/10 1500 10 20.10⁻³ AM/AMPS-90/10 precipitated — (*) The foambreaks almost instantaneously.

This test confirms that the DoTAB and AM/AMPS-90/10 foaming solutionprovides excellent results in terms of foam stability, even in thepresence of salt.

Test 6: Cationic Surfactant DoTAB and Sulfonated PolyacrylamideInfluence of the AM/AMPS-90/10 Copolymer Concentration. DoTAB Polymer VMViscosity VD (mol/l) (ppm) (cm³) (mPa · s) (cm³/min.) 5.10⁻⁵ 100 <1507.3 5.10⁻⁴ 100 <130 2.5 5.10⁻³ 100 1650 0.77 20.6 20.10⁻³ 100precipitated — 5.10⁻⁵ 750 500 3.09 5 5.10⁻⁴ 750 700 3.05 4.6 5.10⁻³ 7501700 1.22 9 20.10⁻³ 750 precipitated — 5.10⁻⁵ 1500 500 46 3 5.10⁻⁴ 1500700 33 3 5.10⁻³ 1500 precipitated — 20.10⁻³ 1500 precipitated —

These results show that even a small polymer concentration (100 ppm) iseffective in stabilizing the foam. By increasing the polymerconcentration (750 ppm to 1500 ppm), the foam that is formed is alsomore stable. Taking into account the strong interactions between polymerand surfactant, the surfactant concentration should be adapted to thepolymer concentration that is used, or vice versa. In this example, itis possible to determine an optimum surfactant concentration of about 510⁻³ mol/l and for a polymer concentration of between 100 and 1000 ppm.

This example clearly shows the synergy between the surfactant and thepolymer and the way of optimizing the foaming solution.

Test 7: Single SDS Anionic Surfactant SDS Polymer VM Viscosity VD(mol/l) (750 ppm) (cm³) (mPa · s) (cm³/min.) 5.10⁻⁵ 0   0 — 1.10⁻⁴ 0   00.9 5.10⁻⁴ 0  500 — 22 1.10⁻³ 0 1700 0.9 21 5.10⁻³ 0 2000 — 13

This test shows that this solution cannot form foam with a lowsurfactant concentration and that at a higher concentration, the foam isless stable (VD on the order of 13 cm³/min). It is noted that themeasurement that is obtained with this surfactant is a little morestable than that obtained with DoTAB (Test 1).

Test 8: Anionic Surfactant SDS and Cationic Polyacrylamide AM/MAPTAC90/10 SDS Polymer VM Viscosity VD (mol/l) (750 ppm) (cm³) (mPa · s)(cm³/min.) 5.10⁻⁵ AM/MAPTAC 90/10 500 — 2.6 5.10⁻⁴ AM/MAPTAC 90/10 600 —5.4 5.10⁻³ AM/MAPTAC 90/10 2200 — 5.1

In this example of foaming composition that comprises an anionicsurfactant and a cationic polymer, it is observed that the addition ofcationic polymer is very beneficial to the formation and the stabilityof the foam that is formed, since a stable foam is formed even with only5 10⁻⁵ mol/l of SDS and that with 5.10⁻³ mol/l of SDS, 2200 cm³ of verystable foam (VD close to 5 cm³/min) is formed.

Test 9: Anionic Surfactant SDS and Cationic PolyacrylamideAM/MAPTAC-75/25. SDS Polymer VM Viscosity VD (mol/l) (750 ppm) (cm³)(mPa · s) (cm³/min.) 5.10⁻⁵ AM/MAPTAC-75/25 450 — 1.8 5.10⁻⁴AM/MAPTAC-75/25 500 — 2.1 5.10⁻³ AM/MAPTAC-75/25 precipitated —

This test shows that with a more charged polymer, the combination of acationic polymer and an anionic surfactant provides very stable foams ata low surfactant concentration. At a higher concentration (in this casegreater than or equal to about 5.10⁻³ mol/l), it is noted that theinteractions are very strong, which produces precipitation.

In general, it should be noted that adding simple electrolytes to thefoaming composition makes it possible to partially screen theinteractions of electrostatic origin. In this case, the surfactantconcentrations can be higher without there being precipitation.

What is claimed is:
 1. A water-based foaming composition that comprisesat least one surfactant and a water-soluble polymer, characterized inthat said surfactant has charges of a sign that is opposite to those ofsaid polymer, said surfactant being present at a concentration of lessthan about 5·10⁻³ mol/l and said polymer being present in aconcentration sufficient to provide a stable foam.
 2. A compositionaccording to claim 1, wherein the surfactant is cationic and in whichthe polymer is anionic.
 3. A composition according to claim 1, whereinthe surfactant is anionic and wherein the polymer is cationic.
 4. Acomposition according to claim 2, wherein the anionic polymer is anacrylamide/acrylamido methane sulfonate copolymer (AM/AMPS), whose levelof the charged portion is between 5 and 40%, and wherein the surfactantis dodecyltrimethylammonium bromide (DoTAB).
 5. A composition accordingto claim 2, wherein the anionic polymer is a natural polymer.
 6. Acomposition according to claim 3, wherein the cationic polymer isAM/MAPTAC, whose level of the charged portion is between 5 and 40%, andwherein the surfactant is SDS.
 7. A process for producing a foam fromwater, at least one surfactant and at least one polymer, wherein asurfactant present in a concentration of less than about 5·10⁻³ mol/land a water-soluble polymer of opposite charge are combined, and thepolymer concentration is determined in order to obtain a stable foamwith the lowest surfactant level possible.
 8. Process according to claim7, wherein the polymer concentration is determined based mainly on thecharge level of the polymer and the surfactant concentration used.
 9. Ina well that is drilled into the ground, circulating a water-basedfoaming composition comprising an anionic surfactant and a cationicwater-soluble polymer wherein the anionic surfactant is present in aconcentration of less than about 5-10⁻³ mol/l.
 10. A compositionaccording to claim 4, wherein said level is between 10 and 25%.
 11. Acomposition according to claim 5, wherein the natural polymer is anegatively modified cellulose derivative.
 12. A composition according toclaim 11, wherein the negatively modified cellulose derivative is CMC.13. A composition according to claim 6, wherein said level is between 10and 25%.
 14. In a well that is drilled into the ground, circulating afoaming composition according to claim 12.